The present disclosure relates to semiconductor memory devices and, more particularly, to flash memory devices.
Flash memory devices that are used as nonvolatile memories are electrically erasable and programmable read-only memories (EEPROMs) in which plural memory blocks are erased or written with data by a one-time programming operation. A general EEPROM has the feature that a memory block is just erasable or programmable in a fixed time. This means that the flash memories operate more rapidly and effectively in reading and writing data when systems employing them read and write data from and into other memory areas at the same time. Flash memories or EEPROMs are usually structurally configured such that insulation films enclosing charge storage elements used for storing data are inevitably worn out after the specific number of operations.
Flash memories store information on their silicon chips even without a power supply being activated. In other words, flash memories are able to retain their information without power consumption even in the face of a power interruption to the chips thereof. Additionally, flash memories offer resistance to physical impulses and a fast access times for reading. With those features, flash memories are generally used as storage units in electronic apparatuses powered up by batteries.